This invention relates to an automatic ink or water quantity adjusting device for an offset press, which automatically adjusts the quantity of ink or water applied to a surface of a printing plate on a plate cylinder.
In general, in an off-set press, ink or water is applied to the surface of a printing plate on the plate cylinder through the fountain roller, the ductor roller and a further group of rollers in the stated order, and printing is correctly carried out by adjusting to a suitable value the quantity of ink or water which is transferred.
Examples of a conventional ink (or water) quantity adjusting device are as shown in FIGS. 1 and 2. For convenience these conventional devices, and the invention which follows, will be described in the context of ink application only, although it should be kept in mind that they are applicable to other fluid transfers such as water.
In the device shown in FIG. 1, a plurality of blades b are moved toward or away from the outer wall of a fountain roller a by an electric motor so that the clearance c therebetween is varied. In the device shown in FIG. 2, the clearance c is adjusted by turning an electric roller d which is in contact with the fountain roller a. That is, in both of the devices, the clearance c is adjusted as required to control the quantity of ink e which adheres to the fountain roller a.
However, these conventional devices are disadvantageous in that small adjustments in clearance will have a large effect on the quantity of ink transferred and on the density of ink on the resulting print. Since it is considerably intricate and difficult to finely adjust the clearance it is extremely difficult to finely adjust the quantity of transferred ink and the print density is often unsatisfactory.